The conditions of Sen Cruz’s birth says that he was born a citizen, has always been a citizen, has never been naturalized and does not need to be naturalized. Title 8 section 1401 subsection G
I don’t know about Canadian law with regards to his kids. To answer your question, one would have to look at Canadian law which has no impact on US law.
He might have also been born with a potential claim or an avenue to American citizenship that other Canadians weren't born with.
However, he or his parents had to claim that citizenship here for that claim to be recognized.
He was born Canadian, in fact and paperwork, and wasn't born with the citizenship paperwork that naturally comes with Natural Born American citizenship.
He had to be naturalized to obtain it, same as in the court cases similar to Ted's situation.
We've been there and done that before and it's called "Naturalized Citizenship".